The present invention relates to waste water treatment methods, as well as waste water treatment equipment, for effectively and simultaneously treating waste water containing hydrogen peroxide, phosphorus and fluorine, and waste water containing organic matters, which are discharged from semiconductor factories, liquid crystal factories and the like.
From the viewpoint of the Water Pollution Control Law, waste water containing hydrogen peroxide and phosphorus in addition to fluorine needs to be treated until the fluorine as well as the hydrogen peroxide and phosphorus that increase the COD (Chemical Oxygen Demand) all come to specified concentrations. Also, the waste water, when containing organic matters, needs to be treated until the organic matters come to a specified concentration.
In this connection, the removal of fluorine is required to meet the regulation value of fluorine concentration. Also, the removal of hydrogen peroxide and organic matters is required to decrease the COD as a regulation value in the treatment water. Further, phosphorus, which causes the red tide, needs to be treated securely until it falls within the regulation value.
Conventionally, in the semiconductor factories and the like, mixed waste water with pH 2-3 containing hydrogen peroxide and phosphorus in addition to fluorine has been treated in the following way. That is, first, fluorine and phosphorus are chemically neutralized with chemicals of slaked lime or the like. After the fluorine and phosphorus have thus been neutralized, sodium bisulfite is added to the treatment water so that hydrogen peroxide is treated by reduction. Otherwise, the treatment water is treated by using a catalyst such as activated carbon or charcoal.
Meanwhile, as fluorine removal equipment for removing fluorine in waste water, one as shown in FIG. 8 is available. In this fluorine removal equipment, fluorine-containing waste water is passed through two calcium carbonate charged tanks 1, 2 so that outflow water of the calcium carbonate charged tank 2 is introduced to a circulation tank 3. Then, the treatment water in the circulation tank 3 is introduced to membrane separation equipment 4, where the treatment water is separated into concentrated water, which contains calcium carbonate crystals flowed out from the latter-stage calcium carbonate charged tank 2, and permeated water. After that, the separated concentrated water is returned to the circulation tank 3. Also, part of the concentrated water is returned to the former-stage calcium carbonate charged tank 1. The permeated water is discharged to a water storage tank 5.
According to this fluorine removal equipment, the fluorine in the waste water reacts with calcium carbonate in the calcium carbonate charged tanks 1, 2, resulting in calcium fluoride. Then, after a specified treatment period has elapsed, the calcium fluoride is pulled out from the calcium carbonate charged tanks 1, 2. Thus, fluorine is removed as calcium fluoride.
As another fluorine removal equipment, calcium fluoride collection equipment as shown in FIG. 9 is available. In this calcium fluoride collection equipment, calcium carbonate in a calcium carbonate silo 7 is added to fluorine-containing solution in a calcium carbonate reaction tank 6. Then, through 50.degree. C.-100.degree. C. high temperature treatment and high-temperature aeration process (or high-temperature pressure reducing deaeration process), calcium fluoride is collected. In addition, reference numeral 8 denotes a blower for aeration, and 9 denotes an air diffuser.
Further, as waste water treatment equipment for treating fluorine waste water containing organic matters, one as shown in FIG. 10 is available. In this waste water treatment equipment, calcium carbonate mineral as a filler material is fluidized strongly or weakly so that both fluorine and organic matters in the treatment water are removed by making good use of chemical reaction and biological reaction of aerobic microorganisms. In addition, reference numeral 11 denotes a first water tank, 12 denotes a second water tank (settling tank), 13 denotes a third water tank (sludge thickening tank), 14 denotes a polyaluminum chloride tank, 15, 16 denote scrapers, 17 to 19 denote blowers, 20 denotes a line mixer, 21 denotes a diffuser, and 22, 23 denote air diffusers. Further, 24a to 24c denote calcium carbonate mineral, 25 denotes inorganic sludge, and 26 denotes microbial sludge.
Further, waste water treatment equipment as shown in FIG. 11 is designed to treat organic-matter-containing fluorine waste water by means of calcium carbonate mineral. In this waste water treatment equipment, the calcium carbonate mineral particles are to be used all in immobilized state. Accordingly, calcium fluoride resulting from reaction of fluorine in the waste water with calcium would remain between immobilized calcium carbonate mineral particles, being present as lumps for a long time. Then, the lumps would grow increasingly larger so as to spread fully in the whole tank, with the result of lowered treatment efficiency. In addition, reference numeral 31 denotes a first reaction adjustment tank, 32 denotes a second reaction adjustment tank, 33 denotes a third water tank (reaction coagulating tank), 34 denotes a fourth water tank (settling tank), 35 denotes a fifth water tank (sludge thickening tank), 36 denotes a filter press, 37, 38 denote water diffusers, 39 to 41 denote blowers, 42, 43 denote air diffusers, and 44, 45 denote scrapers. Further, 46 denotes calcium carbonate mineral, 47 denotes charcoal and 48 denotes a plastic filler material.
Meanwhile, as hydrogen peroxide removal equipment for removing hydrogen peroxide in waste water, there has been available one using granular activated carbon as a catalyst as shown in FIG. 12. This hydrogen peroxide removal equipment has a catalyst part 52 and a settling part 53 in a treatment tank 51. Then, for operation, granular activated carbon is previously charged in the catalyst part 52 at a ratio of 1% to 35% of the effective capacity of the tank. Besides, hydrogen-peroxide-containing waste water is introduced into the treatment tank 51 through a supply port 54. Then, this hydrogen-peroxide-containing waste water permeates into the catalyst part 52, soon filling the interior of the catalyst part 52. On the other hand, the hydrogen-peroxide-containing waste water is introduced into the catalyst part 52 also through a horizontal supply port 55. As a result, a whirling current occurs inside the catalyst part 52, so that the hydrogen-peroxide-containing waste water makes contact with the granular activated carbon so as to be decomposed into water and oxygen through the catalytic action of the activated carbon.
The waste water after the decomposing process overflows the catalyst part 52 to flow into the settling part 53, being discharged through a discharge port 56. In this process, granular activated carbon that has flowed from the catalyst part 52 into the settling part 53 along with the waste water stays within the settling part 53 for a while and settles down, being returned into the catalyst part 52 through an opening 57. Therefore, only supernatant water is discharged through the discharge port 56 of the settling part 53.
This type of hydrogen peroxide removal equipment is used as hydrogen peroxide removal equipment for cases where hydrogen peroxide waste water is discharged alone from production rooms of semiconductor factories. Also, when hydrogen peroxide waste water mixed with phosphorus-containing fluorine waste water is discharged from production rooms, the hydrogen peroxide removal equipment is used in a stage preceding phosphorus-containing fluorine waste water removal equipment as follows:
mixed waste water.fwdarw.hydrogen peroxide removal equipment by activated carbon.fwdarw.phosphorus-containing fluorine waste water removal equipment by slaked lime and coagulants.fwdarw.treated waste water. PA1 a first step for introducing hydrogen-peroxide- and phosphorus-containing fluorine waste water to lower portion of a treatment tank in which reactive filler material has been fluidized in treatment water through aeration by aeration means, while introducing organic-matter-containing waste water to upper portion of the treatment tank so that fluorine is treated through chemical treatment by means of the reactive filler material, and further biologically treating organic matters by means of aerobic microorganisms propagated in a product of the chemical treatment; PA1 a second step for introducing treatment water, which has undergone the first step, into a non-aerating reaction coagulating tank, adding an inorganic coagulant and a high molecular coagulant to thereby treat phosphorus through chemical treatment by the inorganic coagulant, and then coagulating a product of the chemical treatment; and PA1 a third step for introducing treatment water, which has undergone the second step, into a settling tank to thereby separate it into supernatant and sludge, and returning separated sludge to the reaction coagulating tank, wherein PA1 hydrogen peroxide is treated within the reaction coagulating tank by means of anaerobic microorganisms propagated in the returned sludge. PA1 a first tank which has aeration means and to which hydrogen-peroxide-containing waste water and organic-matter-containing waste water are mixedly introduced; and PA1 a non-aerating second tank to which mixed sludge of anaerobic microorganisms and inorganic sludge is introduced and to which treatment water treated by the first tank is introduced, wherein PA1 organic matters are biologically treated by aerobic microorganisms propagated in the first tank, and hydrogen peroxide is biologically treated by the anaerobic microorganisms in the second tank. PA1 a treatment tank which has aeration means and which is filled with a reactive filler material in a state that the reactive filler material is fluidized through aeration by the aeration means, where hydrogen-peroxide- and phosphorus-containing fluorine waste water is introduced to lower portion of the treatment tank while organic-matter-containing waste water is introduced to upper portion of the treatment tank so that fluorine is treated through chemical treatment by the reactive filler material, and further organic matters are biologically treated by aerobic microorganisms propagated in a product of the chemical treatment; PA1 a non-aerating reaction coagulating tank to which treated water from the treatment tank is introduced and further an inorganic coagulant and a high molecular coagulant are added to thereby treat phosphorus through chemical treatment by the inorganic coagulant, and a product of the chemical treatment is reactively coagulated; PA1 a settling tank to which treated water from the reaction coagulating tank is introduced so that sludge in the introduced treated water are settled and separated; and PA1 sludge returning means for returning the sludge settled and separated in the settling tank to the reaction coagulating tank, wherein PA1 hydrogen peroxide is treated within the reaction coagulating tank by means of anaerobic microorganisms propagated in the returned sludge. PA1 a fluorine concentration meter which is placed in the settling tank and which measures fluorine concentration of the treatment water in the settling tank and then outputs a signal representing the measured fluorine concentration; and PA1 addition controlling means for controlling an addition amount of the inorganic coagulant to be added to the reaction coagulating tank based on the signal from the fluorine concentration meter. PA1 hydrogen peroxide concentration measuring means which is placed in the settling tank and which measures hydrogen peroxide concentration of the treatment water in the settling tank and then outputs a signal representing the measured hydrogen peroxide concentration; and PA1 organic-matter-containing waste water introduction controlling means for controlling an introduction amount of the organic-matter-containing waste water to be introduced to the treatment tank based on the signal from the hydrogen peroxide concentration measuring means. PA1 a thickening anaerobic microorganism culturing tank to which sludge settled and separated in the settling tank is introduced to thicken and culture anaerobic microorganisms propagated in the sludge; PA1 sludge returning means for returning the thickened sludge in which anaerobic microorganisms have been thickened and cultured in the thickening anaerobic microorganism culturing tank; PA1 hydrogen peroxide concentration measuring means which is placed in the settling tank and which measures hydrogen peroxide concentration of the treatment water in the settling tank and then outputs a signal representing the measured hydrogen peroxide concentration; and PA1 sludge return controlling means for controlling a return amount of the thickened sludge to be returned to the reaction coagulating tank based on a signal from the hydrogen peroxide measuring means. PA1 a filtering unit to which treated water from the settling tank to filter the treatment water; PA1 a water softener to which treated water from the filtering unit is introduced to remove calcium ions in the treated water; PA1 a reverse osmosis membrane unit to which treated water from the water softener to remove residual ions, residual organic matters, microorganisms and the like in the treated water; and PA1 an ultrapure water system to which treated water from the reverse osmosis membrane unit to produce ultrapure water.
As described above, fluorine-containing waste water discharged in common semiconductor factories where integrated circuits are manufactured has hydrogen peroxide and phosphorus mixed therein. In some other cases, the waste water may be mixed with surface active agents, alcohol, IPA (isopropyl alcohol), acetone or other organic matters. Among such cases, there are some cases where IPA or acetone may be discharged alone. As the reason of this mixing, it could be said that hydrofluoric acid, hydrogen peroxide, phosphoric acid, IPA, acetone and the like are generally used for semiconductor manufacturing processes, where these chemicals are often handled in a clean bench of the same process so that the chemicals may be mixed in fluorine-containing waste water that is discharged in a relatively large discharge amount.
As described above, the most general method for treating the fluorine-containing waste water in which hydrogen peroxide and phosphorus are mixed is to add slaked lime and coagulants and thereby neutralize fluorine and phosphorus. However, with this neutralizing treatment of fluorine and phosphorus by slaked lime or the like, when the fluorine concentration in the treatment water is lowered to the first digit, the aimed fluorine concentration could not be reached without charging extra quantity of slaked lime or coagulants, so that unreacted slaked lime would flow into the settling tank, resulting in increase in generated sludge. This would cause problems of not only increase in generated sludge due to the excessive addition of slaked lime but also increase in costs. Further, because sodium bisulfite is added during the hydrogen peroxide treatment in addition to the excessive addition of slaked lime, the electrical conductivity of the treatment water would increase. Accordingly, there is a further problem that the obtained treated water could not be recycled for the production of ultrapure water.
Thus, as a method for reducing the amount of sludge generated during the treatment of fluorine-containing waste water, there has been developed a method of removing fluorine as calcium fluoride by using calcium carbonate as described before. Moreover, as an advancement of this method, there has been developed a method of removing fluorine and organic matters in the treatment water with the use of calcium carbonate mineral and by using chemical reaction and biological reaction by microorganisms as described before. However, by the former method, hydrogen peroxide, phosphorus and organic matters could not be removed simultaneously with fluorine. Also, by the latter method, hydrogen peroxide and phosphorus could not be treated in itself, disadvantageously.
As equipment for removing hydrogen peroxide in waste water, there has been available hydrogen peroxide removal equipment as shown in FIG. 12. However, since this hydrogen peroxide removal equipment removes hydrogen peroxide by using the treatment with a catalyst of activated carbon and chemicals, there are problems of increases in running cost and initial cost. Furthermore, this hydrogen peroxide removal equipment could not remove fluorine, phosphorus and organic matters.
In addition, as described above, this hydrogen peroxide removal equipment can be used in the former stage of phosphorus-containing fluorine waste water removal equipment in order to treat the waste water in which phosphorus-containing fluorine waste water is mixed in the hydrogen peroxide waste water. This two-stage treatment unfortunately has the following problems.
That is, in general common semiconductor factories, relatively large amounts of organic-matter-containing fluorine waste water are involved. Therefore, even on the assumption that the retention time in the hydrogen peroxide treatment equipment with catalysts of activated carbon or charcoal or the like (of large cost) installed in the former stage is one hour, the amount of retained water is large, causing the hydrogen peroxide treatment equipment to increase in size so that amounts of the activated carbon or charcoal or other chemicals as catalysts increase, resulting in enormous initial cost. Moreover, a large installation area would be required.
Also, since large amounts of retained water within the hydrogen peroxide treatment equipment are involved as described above, large fluctuations of water level in the hydrogen peroxide treatment equipment are involved. Then, because the specific gravity of activated carbon is close to 1, in some cases, a large fluctuation of water level causes part of the activated carbon would flow out so as to flow into the succeeding-stage phosphorus-containing fluorine waste water removal equipment. In this case, activated carbon would adhere to calcium fluoride generated within the calcium-carbonate-mineral-filled tank of the phosphorus-containing fluorine waste water removal equipment, so that calcium fluoride would not flow out from the calcium-carbonate-mineral-filled tank to the succeeding stage. Thus, as calcium fluoride with activated carbon adhering thereto is increasingly deposited, the treatment efficiency in the calcium-carbonate-mineral-filled tank would deteriorate.
In addition, as the preceding stage of the phosphorus-containing fluorine waste water removal equipment, it could be conceived to install equipment for treating hydrogen peroxide by using reducing agents such as sodium bisulfite. In this case, also unfortunately, the running cost would be an enormous one because of the large amount of treatment water. Moreover, a large installation area would be involved.
The above problems in installing the hydrogen peroxide removal equipment at the preceding stage of the phosphorus-containing fluorine waste water removal equipment apply also to the case where hydrogen peroxide and fluorine are continuously treated with activated carbon or charcoal filled in the calcium-carbonate-filled tank 1 of the fluorine removal equipment shown in FIG. 8.
An object of the present invention is therefore to provide waste water treatment method and waste water treatment equipment which can treat hydrogen peroxide, phosphorus-containing fluorine waste water and organic-matter-containing waste water with high efficiency and low cost, simultaneously.
In order to achieve the aforementioned object, there is provided a waste water treatment method characterized by decomposing hydrogen-peroxide-containing waste water by means of anaerobic microorganisms.
With this constitution, hydrogen peroxide as an oxidant is reduced and decomposed by the reducing force of anaerobic microorganisms. Thus, hydrogen peroxide is treated with simple equipment and with low cost without relying on high-priced sodium bisulfite or activated carbon.
Also, there is provided a waste water treatment method characterized by decomposing hydrogen-peroxide-containing waste water by means of mixed sludge of anaerobic microorganisms and inorganic sludge.
With this constitution, the anaerobic microorganisms are entrapped (entrappingly immobilized) by the inorganic sludge, so that the anaerobic microorganisms are protected from dying out by the hydrogen peroxide as an oxidant. Thus, the hydrogen peroxide is effectively decomposition treated by the protected anaerobic microorganisms.
In an embodiment of the present invention, the mixed sludge is sludge introduced from a thickened anaerobic microorganism culturing tank in which anaerobic microorganisms are thickened and cultured.
With this constitution, anaerobic microorganisms that perform decomposition treatment of the hydrogen peroxide are thickened and cultured in the thickening anaerobic microorganism culturing tank. Therefore, the hydrogen peroxide as an oxidant is decomposition treated further effectively by the anaerobic microorganisms having reducibility and high concentration.
In an embodiment of the present invention, the anaerobic microorganisms are bacteria principally comprising sulfate-reducing bacteria.
With this constitution, sulfate-reducing bacteria principally composing the anaerobic microorganisms are easily maintained being cultured and propagated by the anaerobic state being maintained, in hydrogen-peroxide-containing waste water derived from semiconductor factories in which sulfuric acid ions are present at all times.
Also, there is provided a waste water treatment method characterized in that, after introducing hydrogen-peroxide-containing waste water and organic-matter-containing waste water into a first tank, where the mixed waste water is aerated, and then biologically treating the organic matters by means of propagated aerobic microorganisms, introducing the waste water, which has undergone the treatment by the first tank, into a non-aerating second tank into which mixed sludge of anaerobic microorganisms and inorganic sludge has been introduced, and then biologically treating the hydrogen peroxide by means of the anaerobic microorganisms.
With this constitution, organic matters are biologically treated by aerobic microorganisms in the first tank, while hydrogen peroxide is biologically treated by anaerobic microorganisms in the second tank. Thus, both the hydrogen peroxide and the organic matters are biologically treated continuously.
Also, there is provided a waste water treatment method comprising:
With this constitution, in the first step, fluorine is treated through chemical treatment by means of the reactive filler material, and further organic matters are biologically treated by means of aerobic microorganisms propagated in a product of the chemical treatment. Moreover, in the second step, phosphorus is treated through chemical treatment by the added inorganic coagulant, while hydrogen peroxide is treated by the anaerobic microorganisms in the sludge returned from the settling tank. Thus, hydrogen-peroxide- and phosphorus-containing fluorine waste water and organic-matter-containing waste water are simultaneously treated so that fluorine, phosphorus, hydrogen peroxide and organic matters in the treatment water are continuously treated and removed.
In an embodiment of the present invention, the reactive filler material is calcium carbonate mineral, and the inorganic coagulant is slaked lime.
With this constitution, fluorine in the hydrogen-peroxide- and phosphorus-containing fluorine waste water reacts with the calcium carbonate mineral to form calcium fluoride. Also, propagated aerobic microorganisms are entrapped and immobilized to the calcium fluoride, and protected from dying out by the hydrogen peroxide as an oxidant. Thus, organic matters in the organic-matter-containing waste water are decomposition treated effectively by the protected aerobic microorganisms. Then, phosphorus in the hydrogen-peroxide- and phosphorus-containing fluorine waste water is coagulated and settled as calcium phosphate by the added slaked lime. At the same time, residual fluorine is advancedly treated by the slaked lime. Thus, mass generation of sludge can be suppressed by not using slaked lime in the fluorine treatment.
In an embodiment of the present invention, the sludge to be returned is mixed sludge of biological sludge composed principally of the anaerobic microorganisms and calcium fluoride and the slaked lime.
With this constitution, anaerobic microorganisms in the biological sludge returned from the settling tank are entrapped and immobilized to calcium fluoride in the inorganic sludge so as to be protected from dying out by the hydrogen peroxide as an oxidant. Accordingly, when the mixed sludge of biological sludge and inorganic sludge is returned to the reaction coagulating tank, the decomposition treatment of the hydrogen peroxide in the reaction coagulating tank is carried out effectively.
Also, there is provided waste water treatment equipment comprising:
With this constitution, organic matters are biologically treated by the aerobic microorganisms in the first tank, while hydrogen peroxide is biologically treated by the anaerobic microorganisms in the second tank. Thus, both the hydrogen peroxide and the organic matters are biologically treated continuously.
Also, there is provided waste water treatment equipment comprising:
With this constitution, in the treatment tank, fluorine in the hydrogen-peroxide- and phosphorus-containing fluorine waste water is treated through chemical treatment by the reactive filler material. Also, organic matters in the organic-matter-containing waste water are biologically treated by aerobic microorganisms propagated in a product of the chemical treatment. Further, phosphorus in the hydrogen-peroxide- and phosphorus-containing fluorine waste water is treated through chemical treatment by the added inorganic coagulant in the reaction coagulating tank. In the mean time, hydrogen peroxide in the hydrogen-peroxide- and phosphorus-containing fluorine waste water is treated by anaerobic microorganisms in the sludge returned from the settling tank by the sludge returning means. Thus, hydrogen-peroxide- and phosphorus-containing fluorine waste water and organic-matter-containing waste water are simultaneously treated, so that fluorine, phosphorus, hydrogen peroxide and organic matters in the treatment water are continuously treated and removed.
In an embodiment of the present invention, the reactive filler material is calcium carbonate mineral, and the inorganic coagulant is slaked lime.
With this constitution, fluorine in the hydrogen-peroxide- and phosphorus-containing fluorine waste water reacts with calcium carbonate mineral to form calcium fluoride. Also, propagated aerobic microorganisms are entrapped and immobilized to the calcium fluoride so as to be protected from dying out by the hydrogen peroxide as an oxidant. Thus, organic matters in the organic-matter-containing waste water are decomposition treated effectively by the protected aerobic microorganisms. Further, phosphorus in the hydrogen-peroxide- and phosphorus-containing fluorine waste water is coagulated and settled by slaked lime as calcium phosphate. At the same time, residual fluorine is advancedly treated by the slaked lime. Thus, mass generation of sludge is suppressed by not using slaked lime for the treatment of fluorine.
In an embodiment of the present invention, the sludge returned is mixed sludge of biological sludge composed principally of the anaerobic microorganisms and inorganic sludge composed principally of calcium fluoride and the slaked lime.
With this constitution, anaerobic microorganisms in the biological sludge returned from the settling tank are entrapped and immobilized to calcium fluoride in the inorganic sludge so as to be protected from dying out by the hydrogen peroxide as an oxidant. Therefore, when the mixed sludge of biological sludge and inorganic sludge is returned to the reaction coagulating tank, the decomposition treatment of the hydrogen peroxide in the reaction coagulating tank is carried out effectively.
In an embodiment of the present invention, the treatment tank is equipped with a separation chamber for separating the reactive filler material from the treatment water in which the reactive filler material has been fluidized.
With this constitution, the reactive filler material of larger specific gravity that is being fluidized through aeration by the aeration means, and microbial sludge of smaller specific gravity that has been generated through biological treatment with aerobic microorganisms are physically separated from each other by the separation chamber provided in the treatment tank. Thus, unreacted reactive filler material is kept staying in the treatment tank without being introduced to the succeeding-stage reaction coagulating tank together with the treatment water.
In an embodiment of the present invention, the waste water treatment equipment further comprises an inclined plate which is provided in the settling tank and which is inclined so as to interrupt water stream toward the vertical direction within the settling tank.
With this constitution, settlement of the sludge is accelerated by the inclined plate. Also, the anaerobic microorganisms are stuck and immobilized to the whole inclined plate, so that residual hydrogen peroxide and residual organic matters in the treatment water are advancedly treated.
In an embodiment of the present invention, the waste water treatment equipment further comprises:
With this constitution, according to the fluorine concentration of the treatment water in the settling tank, the inorganic coagulant in an amount necessary for the advanced treatment of residual fluorine in the reaction coagulating tank is added to the reaction coagulating tank according to the fluorine concentration of the treatment water in the settling tank. Thus, advanced treatment of residual fluorine is carried out with a necessary least amount of inorganic coagulant, allowing a reduction in the running cost and a reduction in the generation of sludge.
In an embodiment of the present invention, the waste water treatment equipment further comprises:
With this constitution, the amount of organic-matter-containing waste water to be introduced to the treatment tank is controlled responsive to the hydrogen peroxide concentration of the treatment water in the settling tank, so that the amount of organic matters in the treatment tank is controlled. As a result, the amount of anaerobic microorganisms in the settling tank is controlled, so that the treatment water in the settling tank comes to a specified hydrogen peroxide concentration.
In an embodiment of the present invention, the waste water treatment equipment further comprises:
With this constitution, the return amount of thickened sludge to be returned from the thickening anaerobic microorganism culturing tank to the reaction coagulating tank is controlled according to the hydrogen peroxide concentration of the treatment water in the settling tank so that the treatment water in the settling tank comes to a specified hydrogen peroxide concentration.
In an embodiment of the present invention, the waste water treatment equipment further comprises:
With this constitution, fluorine in the hydrogen-peroxide- and phosphorus-containing fluorine waste water is treated without using any large amount of slaked lime and coagulant. accordingly, the electrical conductivity of the supernatant treatment water from which sludge has been settled and separated in the settling tank becomes not more than 700 .mu.s/cm. Therefore, by the treatment water being penetrated successively through the filtering unit, the water softener and the reverse osmosis membrane unit, treated water having such a water quality as enables the production of ultrapure water by the ultrapure water system can be obtained.